V. I. Savchenko

Influence of process conditions on the kinetics of the liquid-phase catalytic hydrogenation of aromatic nitro compounds

Conclusions1.It has been shown that conditions for the liquid-phase catalytic reduction of aromatic nitro compounds have a different effect on the hydrogenation of the nitro compounds to the corresponding arylhydroxylamine and on the disproportionation of the latter with the formation of amines.2.Contrary to the hydrogenation of the nitro group, the disproportionation rate of the arylhydroxylamines depends to a large degree on the temperature and the pH of the medium. Electron-donor substituents increase the disproportionation rate, while electron-acceptor substituents reduce it.3.The conditions have been determined at which an increased yield of arylhydroxy1amines is obtained in the catalytic reduction of the nitro compounds.

Selective hydrogenation of carbonyl group ofα,β-unsatueated aldehydes in the presence of iridium catalyst

α,β-Unsaturated aldehydes (furylacrolein, crotonaldehyde, cinnamaldehyde, citral) are quantitatively hydrogenated to the corresponding unsaturated alcohols in the presence of iridium catalyst. The hydrogenation of acrolein gives a mixture of products, containing mainly allyl alcohol.

Disproportionation of N-arylhydroxylamines in the presence of hydrogenation catalysts and sulfur compound additives

ConclusionsThe yield of N-arylhydroxylamines increases in the liquid-phase catalytic hydrogenation of aromatic nitro compounds due to a reduction in the rate of the secondary transformations of these products upon the introduction of thiophene, sulfolane, and other sulfur compound additives.

Effect of the hydrogen pressure on the kinetics of the liquid-phase catalytic hydrogenation of aromatic nitro compounds

Conclusions1.The relation between the rate of liquid-phase nitro compound hydrogenation and the hydrogen pressure is complex. Over the pressure range from 0.1 to 0.9 MPa, the concentration of the initial nitro product varies in direct proportion to the hydrogen pressure, and this despite the fact that the rate of conversion of the intermediate phenylhydroxylamine into the amino product is unaffected by an alteration in the pressure. This supports the suggestion that the catalytic hydrogenation of nitro compounds proceeds through disproportionation, rather than reduction, of the phenylhydroxylamines.2.The possibility of increasing the selectivity of the hydrogenation reaction for pchlorohydroxylamine formation is discussed, and it is shown that the yield of this product can be increased markedly by working at high pressure and low temperature.

Hydrogenation of aromatic nitro compounds in the presence of an iridium catalyst

1. The hydrogenation of aromatic nitro compounds on an iridium catalyst proceeds rapidly with quantitative yields of the amino products; the catalyst is highly stable in operation. 2. In the hydrogenation of halogen-containing nitro compounds the ratio of the apparent rate constants for hydrogenation and dehalogenation of the nitro compound is much higher than on catalysts examined earlier. 3. The iridium catalyst is potentially useful in the production of halogen-substituted amines by hydrogenation of halonitrobenzenes.